Most manufacturers of gas turbine engines are evaluating advanced multi-walled, thin-walled turbine airfoils (i.e. turbine blade or vane) which include intricate air cooling channels to improve efficiency of airfoil internal cooling to permit greater engine thrust and provide satisfactory airfoil service life.
U.S. Pat. Nos. 5, 295, 530 and 5, 545, 003 describe advanced multi-walled, thin-walled turbine blade or vane designs which include intricate air cooling channels to this end.
In U.S. Pat. No. 5, 295, 530, a multi-wall core assembly is made by coating a first thin wall ceramic core with wax or plastic, a second similar ceramic core is positioned on the first coated ceramic core using temporary locating pins, holes are drilled through the ceramic cores, a locating rod is inserted into each drilled hole and then the second core then is coated with wax or plastic. This sequence is repeated as necessary to build up the multi-wall ceramic core assembly.
This core assembly procedure is quite complex, time consuming and costly as a result of use of the multiple connecting and other rods and drilled holes in the cores to receive the rods. In addition, this core assembly procedure can result in a loss of dimensional accuracy and repeatability of the core assemblies and thus airfoil castings produced using such core assemblies.
An object of the present invention is to provide a multi-wall ceramic core assembly and method of making same for use in casting advanced multi-walled, thin-walled turbine airfoils (e.g. turbine blade or vane castings) which can include complex air cooling channels to improve efficiency of airfoil internal cooling.
Another object of the present invention is to provide a multi-wall ceramic core assembly and method of making same for use in casting advanced multi-walled, thin-walled turbine airfoils wherein a multi-piece core assembly is formed in novel manner which overcomes disadvantages of the previous core assembly techniques.